Drilling machines fit for obtaining vertical or inclined holes in the ground are known.
Said machines are provided with a drilling head that, through the dragger under the head, tows the drilling rod and the covering pipe, also known as jacket.
The drilling head is assembled on a carriage that slides on a vertical or inclinable guide-rail.
A cable or chain is connected, in the upper and in the lower part, with the carriage of the drilling head and slides on two pulleys positioned at the ends of the guide-rail. Said cable or chain is closed as a ring around the guide-rail, around the pulleys and around the carriage of the drilling head and is operated by a proper hydraulic motor and piston.
The sliding of said cable or chain causes the sliding of the carriage and of the drilling head along the guide-rail and consequently the lowering of the drilling head, in order to perform the drilling of the ground, or the lifting of said head in order to extract the drilling rod or in order to realize maintenance operations.
The assemblage of carriage, head, guide-rail is commonly called mast.
The mast, in turn, is constrained by the self-propelled carriage of the machine through a proper support that allows two inclinations:
the inclination of the mast around a horizontal axis perpendicular to the advance direction of the self-propelled carriage;
the rotation of the mast on an axis generically oriented towards the advance direction of the self-propelled carriage.
In short, the support allows the forward inclination of the mast, in order to perform vertical drillings in front of the self-propelled carriage, or inclined perforations in front of the self-propelled carriage even different from a horizontal direction, or the lateral rotation of the mast on the generically vertical plane perpendicular to the advance direction of the self-propelled carriage.
Some drilling machines are provided with a mast support that allows a small lateral translation of the mast itself.
The drilling machines are also provided with levers, mechanism or other device fit for lifting and lowering the mast support, and thus the mast itself, by a short amount.
In some field situations, due to the presence of obstacles and to ground configuration, it is not possible to properly position the self-propelled carriage but it is necessary to utilize supporting structures of the mast equipped on purpose in the site.
There are machines provided with devices for the rotation of the mast about its main axis.
Said machines have the support divided in two parts hinged one to the other on a vertical axis and rotated by two axial and opposed pistons without transmission levers.
The rotation of the mast on said vertical axis is limited at 20-25° on each side because the vertical hinge hinders the extendible rod of the thrusting piston.
When it is desirable to exceed said angle of rotation it is necessary to unconstrain one of the two stems in order to allow the other stem to rotate the system by about 90°.
Said unconstraining action causes a loss of stability and precision in the rotation of the system.